Covering a wall with climbers

Euonymus will self-cling to any wall or fence. 'Silver Queen' and 'Emerald Gaiety' are particularly good varieties

Hydrangea petiolaris is evergreen and has white flowers in the early summer.

There are some clematis that will happily grow on a North wall.
Alpina and Macropetala varieties, Nelly Moser, Wada's Primrose, Dr Ruppel, Mrs Chomondeley, Snow Queen and John Warren. Check them out online to see which will grow to the height you want and also to see the flower colour. My personal favourite is Macropetala Purple Spider.
http://www.clematis-nursery.co.uk/macpsp.JPG2.jpg

I will try euonymus Andrew, it should be nice and bright in Winter too.

The hydrangea I have is this one, Spritzhenry, and its been very slow growing only 30ins. tall so far, but hopefully next year it will romp away, they are such a beautiful climber.

I.m certainly going to try one or two of your clematis Jess, I love the spring flowering ones especially, we have Wisley cream, Willy, and two montana types on the facing south wall and I grew the summer tangutica Radar Love last year. This year I've grown quite a few Korean Beauties, but I think they would need a sunny wall or trellis.

Many thanks everyone for taking the time to read and answer.

Hydrangea petiolaris does take its time to settle in when first planted but after two or three years it will have become established and will romp away.

Thanks for that Xela, I've just had another look at it and it has the aerial roots and healthy growth, it's just small!